NJ002 – Ferox™
Ferox™ Application – Government Facility – New Jersey
Figure 1: ARS field engineer standing by an injection point. The yellow hose conveys the pressurized nitrogen gas while the ZVI slurry is introduced via the blue hose.
The Ferox™ technology was selected as an in situ remedy to treat vinyl chloride (VC) contamination at an active federal government facility located in Morris County, NJ. The facility was placed on the National Priorities List in 1990 as a result of the contaminant levels. The primary contaminant, Vinyl Chloride, was detected at concentrations as high as 739 µg/L in the soils and 1,520 µg/L in the groundwater. Contamination at the site is found primarily in the unconfined aquifer consisting of fine sands, extending to 20 ft. The Ferox™ application at the site included the injection of a special formulation Zero-Valent Iron (ZVI) powder into the subsurface in order to create a 4500-sq. ft. Treatment Zone within a Class 2A aquifer. The Treatment Zone was designed to intercept and dechlorinate VC and other chlorinated volatile organic compounds emanating from an upgradient source area. The layout of the Treatment Zone is shown on the following page and consists of 12 injection points.
More than 10,000 lbs. of Ferox™ ZVI powder in the form of slurry were injected through pre-drilled boreholes into the formation utilizing a pressurized nitrogen gas based delivery system. During injections, pressure influence was seen as far as 40 ft. away from the injection point. Field injection was completed within three weeks, despite adverse winter conditions.
The project is currently under the post-injection monitoring program. Groundwater sampling has been conducted onsite to evaluate the status and rate of dechlorination by the ZVI powder. A data summary table on the following page presents the results of the baseline and the post-injection groundwater sampling events. As evidenced in the table, Post-injection 1 results show an increase in CVOC concentrations for all wells. These temporary increases are commonly observed as the injection process makes connections with hydraulically isolated zones within the formation where residual contamination is located.
As evidence of the dechlorination process, the results of the second post-injection sampling in MW-1B show a decrease in CVOC concentrations and corresponding increases in chloride and iron concentrations. A slight increase in pH is detected in all wells as a result of the oxidation of the ZVI and the dechlorination process. An increase in pH is a commonly observed effect of the ZVI technology. However, unlike the conventional permeable reaction barrier (PRB) technology, the flexibility of the Ferox™ in strategically emplacing designed dosages of the ZVI specific to different portions of the plume can minimize the increase in pH.
Further evaluation included discrete GW sampling using a Hydro-Punch® with the ZVI reaction zone. Eight out of ten of the discrete samples showed 90%+ reduction in the target CVOC.
The results can be found here. (237kb)